Use the following strategy to improve the chance of getting a Kubrow Egg. Play either the "E Prime" or "Eurasia" (recommended) extermination missions. You should find about half a dozen Kubrow dens in them. Equip yourself with the Thief's Wit or Loot Detector mods because Kubrow Eggs appear as resources on the mini-map after being dropped by a Kubrow Den. Additionally, the Carrier's Vacuum precept will be able to collect it when in range. Equipping the Codex Scanner will help locate Kubrow Dens. Kubrow Eggs will have the same golden aura that appear around rare mod drops.